Calibration rig

ABSTRACT

A calibration rig for calibration and/or re-calibration of flow meters ( 5 ) and/or flow meter calibration carts ( 7 ) is described comprising: a source ( 1 ) of pure sterilized water, a piping manifold ( 3 ) connected to the source ( 1 ), at least one flow meter ( 5 ) connected to the source ( 1 ) via the piping manifold ( 3 ) and/or at least one flow meter calibration cart ( 7 ) connected to the source ( 1 ) via the piping manifold ( 3 ) and a drain pipe ( 23 ) connected to each flow meter ( 5 ) and to each flow meter calibration cart ( 7 ) to guide water from the flow meter ( 5 ) and/or the flow meter calibration cart ( 7 ) to a drain ( 23 ).

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] The present invention relates to calibration rigs for calibrationand/or re-calibration of flow meters and/or flow meter calibrationcarts.

[0002] Flow meters are commonly used devices for measuring a flow of aliquid through a pipe. In various branches of industry, for example inthe chemical industry or in the pharmaceutical industry, the measurementdata obtained by flow meters is used to control complex industrialprocesses. Exact measurements of the flow are very important. Thereforeflow meters are carefully calibrated before they are first installed.Also regular re-calibration is performed in order to ensure highaccuracy of measurements over long periods of time.

[0003] Flow meters are currently calibrated on flow meter calibrationrigs comprising a large reservoir of treated city water. The water iscirculated through the flow meter to be calibrated and then to adiverter. The diverter either diverts the water back to the reservoir orto a weigh tank. The weigh tank is used to determine a quantity of waterit obtained from the flow meter and is then emptied into the reservoir.The water supply in the reservoir is reused on the rig many times. Thewater reservoir is completely emptied, cleaned and refilled typicallyonly once a year.

[0004] Problems can occur, when used flow meters are re-calibrated inthis way. Even if all flow meters have been cleaned and decontaminatedbefore re-calibration, it can not be guaranteed that they are absolutelyfree of all hazardous contaminates. First of all it is very difficult todetermine all contaminants the flow meter has been exposed to andsecondly substances that are considered harmless by most users may verywell be considered a dangerous contaminant in another industry. Anexample for this are proteins. Whereas most industries do not considerproteins to be contaminants, they can very well be contaminants in abiological or pharmaceutical process.

[0005] A potentially contaminated flow meter can thus contaminate thewater. This contaminated water can then become a potential source ofcontamination of flow meters that are calibrated or re-calibrated on therig later on.

[0006] The same problems occur when flow meter calibration carts arecalibrated and/or re-calibrated. Flow meter calibration carts are mobileunits designed for on site calibration or re-calibration of flow meters.They comprise a flow meter that is designed to perform a referencemeasurement of a flow on site. Data from this reference measurement isused for calibration and/or re-calibration of the flow meter on thesite. During the process of calibration or re-calibration the flow metercalibration cart is either installed in a pipe leading up to the flowmeter to be calibrated or re-calibrated or it is installed in parallelto the flow meter. In the first case the flow through the flow metercalibration cart and the flow through the flow meter are identical. Inthe second case the flow through the flow meter corresponds to the flowthrough the flow meter calibration cart multiplied by a constant. Thevalue of the constant depends on the mechanical and geometrical featuresof the calibration or re-calibration set up.

[0007] The flow meter to be calibrated or re-calibrated can remain onits position during the entire calibration procedure.

[0008] The flow meter inside the mobile flow meter calibration cartneeds to operate with a high accuracy and reliability. Therefore flowmeter calibration carts have to be calibrated and regularlyre-calibrated, using calibration rigs. Consequently flow metercalibration carts are exposed to the same risks of contamination as flowmeters.

[0009] It is an object of the invention to provide a flow metercalibration rig, that can be used for calibration and/or re-calibrationof flow meters and/or flow meter calibration carts.

[0010] To this end the invention comprises a calibration rig comprising:

[0011] a source of pure sterilized water,

[0012] a piping manifold connected to the source,

[0013] at least one flow meter connected to the source via the pipingmanifold and/or

[0014] at least one flow meter calibration cart connected to the sourcevia the piping manifold and

[0015] a drain pipe connected to each flow meter and to each flow metercalibration cart to guide water from the flow meters and/or the flowmeter calibration carts to a drain.

[0016] According to a refinement of the invention, a calibratedreference flow meter is installed in parallel or alternatively in seriesto a flow meter or a flow meter calibration cart to be calibrated orre-calibrated.

[0017] According to a refinement of the invention a device for measuringa quantity of water received from a flow meter or a flow metercalibration cart is installed between the flow meter or the flow metercalibration cart and the drain pipe.

[0018] According to another refinement of the invention a device forsupplying a predetermined quantity of water is installed between thesource and the flow meter or the flow meter calibration cart. Preferablythe device for measuring a quantity of water is a weigh tank.

[0019] Further the invention comprises a method of calibration orre-calibration of a flow meter or a flow meter calibration cart,comprising the steps of

[0020] mounting the flow meter or the flow meter calibration cart on aflow meter calibration rig according to the invention,

[0021] sending a quantity of pure sterilized water through the flowmeter or the flow meter calibration cart,

[0022] directing the water from the flow meter or the flow metercalibration cart to a drain.

[0023] One advantage of the calibration rig is that even if calibrationor re-calibration of contaminated flow meters or flow meter calibrationcarts is performed a contamination of the rig cannot occur. Thussubsequently calibrated or re-calibrated devices cannot becomecontaminated.

[0024] Since the water is pure and sterilized and never resupplied tothe rig a decontamination of flow meters or flow meter calibration cartsis no longer necessary prior to re-calibration.

[0025] The invention and further advantages are explained in more detailusing the figures of the drawing, in which one exemplary embodiment isshown.

BRIEF DESCRIPTION OF THE DRAWING

[0026]FIG. 1 shows a schematic diagram of calibration rig according tothe invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 shows a schematic diagram of a calibration rig according tothe invention. It comprises a source 1 of pure sterilized water.Extremely pure sterilized water is for example known as water forinjection and is commonly available, for example from a Water forInjection (WFI) system. The source can be a container or vessel of anykind that is capable of holding large quantities of water, for exampleseveral thousand or even hundred thousand liters.

[0028] A piping manifold 3 is connected to the source 1. The pipingmanifold 3 comprises at least one connector designed for connecting aflow meter 5 or a flow meter calibration cart 7 to the source 1.Calibration or re-calibration is performed by the method of mounting theflow meter 5 or the flow meter calibration cart 7 on a flow metercalibration rig according to the invention. In a next step puresterilized water is send from the source 1 through the flow meter 5 orthe flow meter calibration cart 7 and is finally left to drain before orafter measuring its exact quantity. Pure sterilized water contains nocontaminants of any kind. It cannot contaminate the devices that arecalibrated or re-calibrated using the calibration rig. The water isalways left to drain and never re-used for calibration or re-calibrationpurposes. Consequently even contaminated flow meters 5 or flow metercalibration carts 7 cannot cause contamination of subsequentlycalibrated or re-calibrated devices. Even if contaminants dissolve inthe water they will always be guided downstream of devices to becalibrated or re-calibrated in the future.

[0029] In the embodiment shown in FIG. 1 the piping manifold 3 comprisesa diverter 9 that links the source 1 to one or more pipes 11, 12, 13,15. Valves 17 are foreseen at an end of each pipe 11, 12, 13, 15 nearthe diverter 9. By opening and closing the individual valves 17 a flowof water is directed into one or more of the pipes 11, 12, 13, 15. Inthe embodiment shown, a first pipe 11, a second pipe 12, a third pipe 13and a fourth pipe 15 are connected to the diverter 9.

[0030] The first pipe 11 leads up to a t-junction 19. A flow meter 5 ora flow meter calibration cart 7 to be calibrated or re-calibrated isconnected to one end of the t-junction. A calibrated reference flowmeter 21 is connected to an other end of the t-junction 19. Water fromthe source is directed through the pipe 11 and the t-junction 19 and fedthrough the flow meter 5 or the flow meter calibration cart 7 andthrough the calibrated reference flow meter 21.

[0031] For calibration or re-calibration purposes the calibratedreference flow meter 21 is installed in parallel to the flow meter 5 orthe flow meter calibration cart 7 to be calibrated or re-calibrated. Itmeasures the flow through the calibrated reference flow meter 21. Dataobtained from this measurement is then used to calibrate or re-calibratethe flow meter 5 or the flow meter calibration cart 7 installed parallelto the calibrated reference flow meter 21. The flow through thecalibrated reference flow meter 21 is equal to the flow through the flowmeter 5 or the flow meter calibration cart 7 multiplied by a constant.That constant is determined by the mechanical and geometrical propertiesof the calibration rig, the calibrated reference flow meter 21 and theflow meter 5 or the flow meter calibration cart 7 to be calibrated orre-calibrated. It can be determined experimentally.

[0032] A drain pipe 23 is connected to the flow meter 5 or the flowmeter calibration cart 7. A drain pipe 25 is connected to the calibratedreference flow meter 21. The drain pipes 23, 25 guide the water from theflow meter 5 or the flow meter calibration cart 7 and from thecalibrated reference flow meter 21 to a drain 27.

[0033] The second pipe 12 leads up to a flow meter 5 or a flow metercalibration cart 7. Downstream of the flow meter 5 or the flow metercalibration cart 7 a calibrated reference flow meter 21 is installed inseries to the flow meter 5 or the flow meter calibration cart 7 to becalibrated or re-calibrated. Thus the flow through the reference flowmeter 21 is equal to the flow through the flow meter 5 or the flow metercalibration cart 7 and is used for the calibration or re-calibration. Adrain pipe 23 is connected to the reference flow meter 21 directing thewater supplied by the source 1 to the flow meter 5 or the flow metercalibration cart 7 to the drain 27.

[0034] It is also possible to install the reference flow meter 21upstream of a device to be calibrated or re-calibrated.

[0035] A flow meter 5 or alternatively a flow meter calibration cart 7is connected to the third pipe 13. Again a drain pipe 23 is connected tothe flow meter 5 or the flow meter calibration cart 7, directing thewater supplied by the source 1 from the flow meter 5 or alternativelythe flow meter calibration cart 7 to the drain 27.

[0036] Here a device 29 for measuring a quantity of water received fromthe flow meter 5 or the flow meter calibration cart 7 is installedbetween the flow meter 5 or the flow meter calibration cart 7 and thedrain pipe 23. One example of such a device 29 is a weigh tank. A weightank measures the weight of a medium it contains. By measuring theweight of the water that flowed through the flow meter 5 or the flowmeter calibration cart 7 into the weigh tank and the time needed for thewater to flow through the flow meter 5 or the flow meter calibrationcart 7 an average flow can be calculated and applied in the calibrationor re-calibration process.

[0037] Yet another calibration set-up is shown which is connected up tothe fourth pipe 15. A flow meter 5 or alternatively a flow metercalibration cart 7 is connected to the fourth pipe 15. Again a drainpipe 23 is connected to the flow meter 5 or the flow meter calibrationcart 7, directing the water supplied by the source 1 from the flow meter5 or alternatively the flow meter calibration cart 7 to the drain 27.

[0038] Downstream of the flow meter 5 or the flow meter calibration cart7 a diverter 31 is foreseen. The diverter 31 can either be set to form adirect connection to the drain pipe 23 or it can be set to direct thewater to a device 29 for measuring a quantity of water received from theflow meter 5 or the flow meter calibration cart 7, which in turn isconnected to the drain pipe 23. The device 29 shown is a weigh tank,that can be used for calibration or re-calibration as previouslyexplained.

[0039] In a setting where the diverter 31 connects the flow meter 5 orthe flow meter calibration rig 7 up to the drain pipe 23, the flowthrough the flow meter 5 or the flow meter calibration rig 7 can bedetermined by measuring the time it takes for a predetermined quantityof water to go through. Preferably a device 33 for supplying apredetermined quantity of water is installed between the source 1 andthe flow meter 5 or the flow meter calibration cart 7 respectively. InFIG. 1 the device 33 comprises a container 35 with an accurately knowninner volume that can be filled by the source 1 and drained completelyinto the third pipe 15. Filling and draining of the container iscontrolled by a first valve 37 located immediately upstream of thecontainer 35 an a second valve 39 located immediately downstream of thecontainer 35.

[0040] Whenever the device 33 is not needed, the first and the secondvalve 37, 39 can be opened completely, allowing the water from thesource 1 to flow trough. Preferably the device 33 is positioned upstreamof the diverter 9, in order to allow use of the device 33 in combinationwith any of the calibration set-ups foreseen on the rig.

[0041] Calibration set-ups as the ones connected to the first, thesecond, the third and the fourth pipe 11, 12, 13, 15 form examples forsuch set-ups. A calibration rig according to the invention can compriseany number each of these set-ups or even modifications thereof as longas only pure sterilized water enters the devices to be calibrated orre-calibrated and is left to drain once it has been directed through adevice to be calibrated.

What is claimed is:
 1. A calibration rig comprising: a source (1) ofpure sterilized water, a piping manifold (3) connected to the source(1), at least one flow meter (5) connected to the source (1) via thepiping manifold (3) and/or at least one flow meter calibration cart (7)connected to the source (1) via the piping manifold (3) and a drain pipe(23) connected to each flow meter (5) and to each flow meter calibrationcart (7) to guide water from the flow meter (5) and/or the flow metercalibration cart (7) to a drain (23).
 2. Calibration rig according toclaim 1, wherein a calibrated reference flow meter (21) is installed inparallel to a flow meter (5) or a flow meter calibration cart (7) to becalibrated or re-calibrated.
 3. Calibration rig according to claim 1,wherein a calibrated reference flow meter (21) is installed in series toa flow meter (5) or a flow meter calibration cart (7) to be calibratedor re-calibrated.
 4. Calibration rig according to claim 1, wherein adevice (29) for measuring a quantity of water received from a flow meter(5) or a flow meter calibration cart (7) is installed between the flowmeter (5) or the flow meter calibration cart (7) and the drain pipe(23).
 5. Calibration rig according to claim 4, wherein the device (29)for measuring a quantity of water is a weigh tank.
 6. Calibration rigaccording to claim 1, wherein a device (33) for supplying apredetermined quantity of water is installed between the source (1) andthe flow meter (5) or the flow meter calibration cart (7).
 7. Method ofcalibration or re-calibration of a flow meter (5) or a flow metercalibration cart (7), comprising the steps of mounting the flow meter(5) or the flow meter calibration cart (7) on a flow meter calibrationrig according to one of the previous claims, sending pure sterilizedwater through the flow meter (5) or the flow meter calibration cart (7),and directing the water from the flow meter (5) or the flow metercalibration cart (7) to a drain (23).